To study the growth characteristics, histochemical and biochemical reactivities, immunologic properties, and electronmicroscopic and autoradiographic details of human and animal skeletal muscle and animal neurons grown in tissue culture. To perpetuate abnormalities of human cells (muscle, schwann cells, fibroblasts) in culture, or to induce those abnormalities in cultured normal human or animal tissues. To compare the growth and histochemical characteristic of "red" vs. "white" muscle in culture. To study interactions between lower motor neurons and muscle fibers in culture. To seek growth-inhibitory ("toxic") factors in body fluids of our patients, using cultured neurons or muscle cells as test objects. The tissue is from either normal or abnormal biopsied adult or child human tissue, especially muscle, or from normal chick, mouse or rat embryos.